This invention is in the field of highway trailer brakes, and in particular the maintenance and repair thereof.
Highway trailer brakes are the subject of increasing scrutiny from those responsible for highway safety. RockwellJ and Pro-ParJ are two of the more common brands of trailer axle assemblies. These assemblies incorporate an axle stub at each end thereof for attachment of a wheel via bearings and so forth. At each thereof there is also mounted a xe2x80x9cspiderxe2x80x9d which provides brake assembly holes to hold the brake mechanism in the proper location relative to the axle stub. On one side of the axle stub a cam shaft, for moving the brakes, passes through a cam shaft hole in the spider. On the opposite side are two anchor pin holes where the brake shoes are retained. The rotating action of the cam shaft causes the brake shoes to pivot in the anchor pin holes and move relative to the brake drum located on the wheel, thereby applying or releasing the brakes.
The proper location and size of the cam shaft and anchor pin holes is critical to proper brake operation and performance. The holes are bushed, and the bushings may be replaced periodically, however eventually the holes become worn so that the replacement bushings are loose in the holes. The brakes then will have excessive play in them, and will not operate satisfactorily.
Conventionally, the axle is replaced, or alternatively the spider may be cut off and a new spider installed. Removing the old spider and installing a new one is time consuming and strenuous, since the wheels, brakes and shafts must be assembled on the axle to ensure that the new spider is properly located; the new spider is then tacked in place, and the wheels, brakes and shafts removed so that the new spider may be welded in place. The entire process takes several hours for skilled workers to complete.
It is the object of the present invention to provide a method and apparatus for repairing the cam shaft and anchor pin holes in RockwellJ, Pro-ParJ or similar trailer axle assemblies which does not require replacement of the spider, but rather repairs the holes in the original spider.
A boring tool is located at the proper distance from, and in alignment with, the axle and bores slightly over-size holes in the spider with the centers thereof in the same location as the centers of the original holes and at substantially the same location as the worn out holes. The extra diameter overcomes the distortion of the worn holes, providing a cylindrical unworn hole which properly accommodates an oversize outside diameter bushing with the same inside diameter as the original. The shafts are thus held in their proper location relative to the axle, and play is eliminated. The apparatus provided for practicing the method is convenient and allows for completion of the repair in substantially less time than is required to replace the spider.